[llvm] Reduce shl64 to shl32 if shift range is [63-32] (PR #125574)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Should I generalize the reduction to include shl32 -> shl16?
 
I would prepare to generalize it, but do the reduction as a separate step 

https://github.com/llvm/llvm-project/pull/125574